In general, in information electronic appliances, a switching mode power supply (hereinafter, referred to as an SMPS) having a high efficiency and a small capacity in comparison with a non-switching power supply is widely used as a power supply unit. Even in a standby mode, that is, a state where the electronic appliance does not perform the essential functions, the SMPS is maintained to be in an operation state in order to supply power. Therefore, even in the standby mode, the SMPS consumes a relatively large amount of power.
An existing SMPS controls a gate signal of a MOSFET functioning as a switch by using a PWM signal generator to perform the functions. In the related art for reducing the standby power, an amount of power consumption is reduced by reducing the number of times of switching by using a signal skip method where a PWM signal according to a change in source current of the MOSFET or a feedback signal fed back from a load is not allowed to be generated at a larger period than regulation of an existing pulse width.
However, in the case where the power consumption at the load stage is small, the method of reducing an amount of power consumption by reducing the number of times of switching of the PWM signal, that is, a gate signal of the MOSFET is used. Although the amount of power consumption is reduced in comparison with a normal operation, the switching is maintained at a certain interval, and thus, the SMPS is allowed to continuously operate, so that a certain amount of power is continuously consumed.
In addition, in order to lower the standby power of a large-capacity SMPS or the like, various methods of additionally installing a small-capacity auxiliary SMPS or the like have been attempted. Particularly, in the case where the SMPS is applied to a large-capacity LED illuminating device, there is an increasing need to lower the standby power.
FIG. 1 is a diagram illustrating a configuration of a general SMPS for driving an LED illuminating device as an example of the related art of consuming a standby power.
Referring to FIG. 1, included are an AC power supply unit 10 which supplies a AC voltage, an SMPS 30 which rectifies and switches the AC voltage supplied from the AC power supply unit 10 and supplies a power, an LED illuminating device 40 which emits light by using the power supplied from the SMPS 30, and a central control server 60 which controls the LED illuminating device 40.
Herein, the SMPS 30 includes an AC-DC rectifier circuit 32, a switching unit 33, a transformer 34, a DC-DC rectifier circuit 35 and a control unit 36, and supplies the output DC power to the LED illuminating device 40.
The AC-DC rectifier circuit 32 removing noise from an AC voltage supplied from the AC power supply unit through filtering, converts the AC voltage to a DC voltage, and outputs the DC voltage to the switching unit 33.
The switching unit 33 performs switching at a frequency of several tens kHz to several MHz by using an element such as a high-withstand-voltage TR, an MOSFET, and an IGBT and outputs the voltage to the transformer 34.
The transformer 34 is determined according to a use frequency and a magnitude of a use power and outputs to the DC-DC rectifier circuit 35.
The DC-DC rectifier circuit 35 converts the DC power which is converted according to a switching control signal input from the control unit 36 to an appropriate power and supplies the appropriate power to the LED illuminating device 40.
At this time, in a standby mode where power supply to the LED illuminating device 40 is unnecessary, an output of an unnecessary portion of the DC-DC rectifier circuit 35 and a secondary coil (not shown) of the transformer 34 is blocked or reduced under the switching control of the control unit 36, so that power supply to the parts to which power supply is unnecessary in the standby mode is blocked or reduced.
However, in this case, in the standby mode, power supply to the SMPS is continuously performed, and thus, power is continuously consumed in the control unit 36 and the DC-DC rectifier circuit 35. Therefore, there is a problem in that a considerable amount of a standby power is consumed.